Hello Brendan,
I'm going for Japanese Sparrowhawk: from what I've seen of Crested Goshawks, they show thicker talons, a longer bill, and bulkier build than in this bird. Besra juveniles tend to have thicker stripes on the abdomen, while young Japanese Sparrowhawks tend to show round spots on the belly as in this bird. Also Besra doesn't seem to migrate much, but Japanese Sparrowhawks certainly do - and thus turn up on offshore islands more frequently I guess.
In any case, it's still very exciting to have an accipiter to land right on top of your head
!!
